Fluidized catalytic cracking (“FCC”) is a key process in modern petrochemical refineries due to the large volume of gasoline and distillate fuels that it generates. An integral part of FCC operation is the catalyst, which is particularly designed in view of a unit's product needs, feedstock and operating limitations. The health of the FCC catalyst is typically monitored by taking samples of the circulating catalyst (the so-called equilibrium catalyst) and performing tests to measure physical/chemical properties and the activity of the catalyst under standard laboratory testing. However, the properties of the equilibrium catalyst (“ECAT”) also provides a measure of the deactivation characteristics of a particular FCC unit, which is a complex product of hydrothermal conditions, catalyst additions, inherent catalyst activity and stability, and catalyst metals levels. Understanding a unit's deactivation characteristics, however, is a key consideration when a refiner undertakes changing its FCC catalyst, since it is customary for catalyst manufacturers to test new catalyst candidates by deactivating the candidates under conditions that proximate those of the unit ECAT. The closer that a laboratory unit deactivation protocol is to the actual unit, the more confidence can be given to test results that compare new catalysts to the incumbent catalyst.
When conducting a catalyst study, it is customary to obtain a sample of the unit feedstock and ECAT. Often fresh catalyst samples of the current catalyst are also available. The fresh catalyst is metallated and deactivated under laboratory conditions to duplicate the catalyst deactivation in the unit. In particular, the catalyst manufacturer attempts to duplicate the ECAT total surface area, zeolite surface area, matrix surface area and unit cell size with the deactivation protocol used in an accelerated manner relative to unit deactivation. Those conditions are then used to deactivate the proposed catalysts, and catalyst performance testing is conducted on the deactivated catalysts with the unit feedstock.
Early deactivation methods did not utilize metals at all, or deactivated the metals in a way that overemphasized their dehydrogenation effects. This was not as serious a concern to units that operated at low metals levels, and in those cases the total surface area, and especially zeolite surface area would be targeted to more closely match the unit ECAT. However, for higher metals operation it was clearly inadequate. Much work has been done to improve deactivation methods. For example, studies have been performed in the area of cyclic propylene steaming, e.g., Wallenstein et al., Recent advances in the deactivation of FCC catalysts by cyclic propylene steaming (CPS) in the presence and absence of contaminant metals, Applied Catalysis A: General 204 (2000) 89-106, Wallenstein et al., Review on the deactivation of FCC catalysts by cyclic propylene steaming, Catalysis Today 127 (2007), 54-69, Psarras et al., Investigation of advanced laboratory deactivation techniques of FCC catalyst via FTIR acidity studies, Microporous and Mesoporous Materials 120 (2009) 141-146, Nguyen et al., Effect of hydrothermal conditions on the catalytic deactivation of a fluid cracking catalyst, Reac. Kinet Mech. Cat. (2013) 109:563-564, and Psarras et al., Advanced Artificial Deactivation of FCC Catalysts, from Chemical Industries (Boca Raton, Fla.) (2010), 129 (Advances in Fluid Catalytic Cracking), 127-141. However, despite the development of protocols that better simulate metals effects and match zeolite surface areas, the ability to adequately reproduce matrix surface area, in particular to simultaneously match zeolite and matrix surface area, has remained elusive, since the severity required in conventional protocols to match matrix surface areas will normally reduce the zeolite surface area to undesirable levels.
The need to deactivate FCC catalysts in such a way as to match matrix surface area has thus existed for many years, however, as the advance of higher matrix catalysts has accompanied the rise in importance of bottoms upgrading and maximum LCO operation, the need to adequately match all catalyst properties has also grown. There is thus an ongoing need for improved catalyst deactivation protocols, and in particular, a need for catalyst deactivation protocols that can independently adjust matrix surface areas in porous solids relative to zeolite surface area in such a way that both the zeolite surface area and matrix surface area of a commercial ECAT can be duplicated from laboratory deactivation methods. Applicants have unexpectedly discovered methods of achieving such a laboratory deactivation using cyclic deactivation methods.